Recombinant alpha 1-antitrypsin is currently administered intravenously in the treatment of cystic fibrosis. A new protocol has been designed to treat patients with this condition via aerosol so as to deliver large doses of alpha-1 antitrypsin directly to the respiratory tract. We will study the particle size distributions of several nebulizers to ensure that the proper particle size (1-3 microns) is being delivered to the patient. The Malvern particle sizer (Model 2600C, Malvern Inc.,- South Borough, MA) was purchased and used to perform several preliminary studies. The Misty, Retec, Vortran, Ultravant and Pari-Boy nebulizers were evaluated. Further studies will involve a more in-depth analysis of the drugs and nebulizers. Some of the nebulizers were found to consistently produce particles in the range for aerosol administration.